Vol. 1, No 3, 1996 pp.
256 - 264
UDC
547.1-316
STEREOSELECTIVE REDUCTIONS OF THE SOME METHYL KETONES FROM BICYCLO[2.2.1]HEPTANE AND BICYCLO[2.2.2]OCTANE SYSTEM
S. Sukdolak1, S. Solujić1, G. Stojanović2
1 Department of Chemistry, Faculty of Science, P. Box 60, 34000 Kragujevac, Yugoslavi
2 Department of Chemistry, Faculty of Science, Ćirila i Metodija 2, 18000 Niš, Yugoslavia
Abstract.
In the reactions of racemic endo-2-acetyl-bicyclo[2.2.1]heptene (I), endo-2-acetyl- bicyclo[2.2.1]heptane (IV) and endo-2-acetyl-bicyclo[2.2.2]octane (V), with the many of variety reducing agents, endo-α-methyl-2-methanols with the 2S, αR or 2R, αS configuration (II) were always formed in excess over the corresponding diastereomeric endo-alcohol (III) with the 2S, αS or 2R, αR configuration. In these nucleophilic additions stereoselectivity was low for the reducing agents NaBH4 and LiAIH4 but increased when the reducing reagents with bulky groups were used, i.e. R3BH, B2H6 and R3AIH. Steric control of these 1,2-asymetric reduction is discussed in terms of the open-chain transition models of the Cram and Karbatsos type.
STEROSELEKTIVNOST REDUKCIJA ENDO-METIL KETONA BICIKLO[2.2.1]HEPTANSKE I BICIKLO[2.2.2]OKTANSKE SERIJE
U reakcijama redukcije endo-metil ketona biciklo[2.2.1]heptanske i biciklo[2.2.2]oktanske serije sa različitim redukcionim agensima dobiveni su odgovarajući stereoizomerni endo-α metil-2-metanoli. Konformer 2S, αR ili 2R, αS je dobiven uvek u višku u odnosu na 2S, αS ili 2R, αR konformer. Sterna kontrola ovih 1,2-asimetričnih redukcija je diskutovana i tumačena primenom Cram-ovog i Karabatsos-ovog pravila.
